1. Field of the Invention
This invention relates generally to robotically controlled underwater vehicles or "Remote Operated Vehicles" (ROV'S), and more particularly to an underwater self-propelled surface-adhering robotically operated vehicle capable of being navigated through a volume of water and of attaching itself to an underwater surface and traversing along the surface and having an evacuable enclosure providing an environment for task accomplishment and having measurement and inspection devices and tools for underwater hull cleaning, welding, and other underwater tasks.
2. Brief Description of the Prior Art
Heretofore, most robotic underwater vehicles designed for underwater inspections have been designed primarily for mid-water use without having the capability to remain attracted to a surface while transiting along it or closely following its curvature for inspection purposes. This inherent lack of capability prevents or limits these machines in station keeping ability in high current or surge conditions while operating. Because these inspection or viewing machines may be required to hold station for long periods of time while task accomplishmment or inspections are underway, this is a serious limitation which the present invention overcomes. The advantages gained by an ROVS' attachment to the work piece are so great that an entire technology base producing a host of new, heretofore unaccomplishable underwater task capabilities is now enabled.
In addition, there are several other related needs, such as the need for an ROV mounted movable enclosure with one open side sealed against the work which can be used as an environment to complete tasks which do not work well underwater such as painting, welding and thermal spraying, as well as other tasks, and can provide unparalleled solutions to underwater problems heretofore unsolvable. These needs have remained largely unrecognized and therefore unanswered until now.
A past unmet need is that of an inspection vehicle which will produce highly reliable mapping and inspection data for underwater structures and for damage to ships, which can adhere to the surfaces of the structure and uses some type of reference method, such as acoustic pingers to assist in precise location at all times. In the past this type of inspection was undertaken using free swimming ROV's or divers with pingers primarily using visual cues to discover and determine damage extent and location. This method has proven to be time consuming and suffers from a lack of accurate mapping and locational data regarding the nature and extent of damage and underwater conditions. In addition, it suffers from the inability to non-destructively and visually inspect large areas of the submerged structure in a timely manner.
One specific case in point of a technological breakthrough in an area of heretofore unrecognized need is disclosed using the present invention as a surface adhering work platform with sufficient attractive force to remain attached to a submerged structure during severe wave and current loading with virtually no unwanted movement. This attribute makes this invention the preferred type of operating platform for intricate tasks such as 3-D laser mapping and underwater robotic welding operations. Another heretofore unrecognized need is for an ROV with built in purgable buoyancy enclosure(s), called buoyancy tubes, which may be used to assist in increased buoyancy and assist in the ROVs orientation. And still another heretofore unrecognized need is that of a stationary, firmly attached vehicle which has excavation tools attached which can enable it to remove soil from around and underneath an underwater pipeline without the need for divers in offshore pipeline repair and inspection operations.
Relative to underwater vehicles and tools which are capable of attaching themselves to objects and surfaces underwater, which is a prerequisite for robotic control, guidance, and navigation of an evacuable enclosure with one open side while attached to the surface, there has been little or no advancement. Most ROV'S are use limited in that they are not designed to attach themselves to a work surface underwater and traverse it, with several exceptions, which follow. The most notable exception to this limitation is disclosed in U.S. Pat. No. 3,906,572 by Winn. This apparatus, which is known under the trade name of SCAMP, has been in widespread worldwide use for underwater hull cleaning of ships hulls since the late 1960's. While it does remain attracted to the hull of a ship while in use, SCAMP suffers from the major drawback of not having any navigation or guidance aids such as thrusters or rudders incorporated to make it capable of being robotically controlled while in transit thru a volume of water to the side of the ship's hull from the hull cleaning support platform or dock. It must be guided by a diver or swimmer to the ship's hull because of its inherent instability and lack of controllability in free water. As such, it is not a true "ROV", but instead is simply a robotically controlled work tool for the side of ships and other marine structures. The teachings of Winn's disclosure reflect this limitation, and no reference to thrusters, water jets or other mid-water guidance features such as a rudder are mentioned or suggested. Since it is physically impossible for a single impeller or propeller driven underwater tool to guide itself without some external means of guidance or directional stability, this is a significant drawback which the present invention overcomes. A similar invention, U.S. Pat. No. 5,174,222 by Rogers, shows a similar hydraulically powered robotic or diver guided vehicle which suffers from the same inherent drawbacks. In addition, these two machines do not have an evacuable area or enclosure incorporated as designed.
Another prior art invention which has the ability to attach itself to underwater structures is disclosed by the same author, Winn, in a subsequent patent. U.S. Pat. No. 4,058,082 discloses an underwater painting machine with the same basic structural design for maintaining it attached to the ship's hull. Although this machine has a different purpose, that of painting instead of cleaning ship's hulls, with attendant structural differences, it suffers from similar limitations in guidance and navigation capabilities to that of SCAMP.
Another prior art invention which is capable of attachment to a substrate with an incorporated evacuable enclosure is disclosed in U.S. Pat. No. 4,270,484 by Shimatani, et al, which discloses an underwater painting machine which has a painting chamber incorporated which is evacuable. In this invention, the machine can be held against a work surface principally by electromagnets, and uses as a backup attraction method a thruster which does not produce a low pressure area underneath the machine body as in the prior art of Winn or Rogers, above, and with the present invention, and suffers from the additional limitation of not being equipped with guidance thrusters or other directive and navigational means. Additionally it has wheels of conventional design which do not have a large contact area to influence movement of an incorporated evacuable enclosure, creating an unreliable traction method for this type of structural design. In a major structural defect, the evacuable enclosure is rigid in its attachment to the main body of the machine, and uses the inflatability of a seal at the bottom of the painting chamber, which is the evacuable enclosure of the invention, as the method of conforming to irregularities in the substrate. Because many irregularities exceed in size the capabilities of a seal to conform, effectively jamming the machine in place or flooding the evacuable enclosure, or both when coming in contact with it, this design is structurally deficient and limited to very even underwater surfaces, making the capabilities of this machine limited. Additionally, the ballast chambers incorporated do not have the ability to allocate either or both ballast and buoyancy to specific areas of the machine to compensate for its physical position and dynamic buoyancy changes, making it structurally unsuitable for adaptation to robotic guidance and navigation capabilities. Also, this machine's design is limited to the specific function of underwater painting.
Another prior art hull cleaning machine which has the ability to remain attracted to the hull of a ship, and which is a true ROV, is disclosed in Japanese patent No. 0299492 by Miyama, which shows a machine with a frame which encloses several thrusters which act to push the machine against the hull of the vessel constantly while the machine cleans the hull, and which rolls along the hull on wheels provided which are motorized. This vehicle employs a minimum of two thrusters to keep the machine against the hull instead of an impeller in an enclosed suction chamber, and does not employ a closed body with a low pressure area below the thrusters to create attraction to the hull. As such, it is structurally different from the present invention and as a result is not capable of creating strong attraction forces against the hull by creating a proximal partial vacuum or low pressure area while attached to a surface. The thruster's thrust remains fairly constant whether attracted to the hull or in mid water transiting to a location.
In the past when hull cleaning operations were undertaken the liquid effluent and solid marine growth cleaning products were simply discharged back to the sea and allowed to settle to the sea floor. Research has shown that marine algae and other marine organisms which are attached to ship hulls absorb and store large amounts of copper compounds from hull coatings, making discharge of this matter to the sea floor questionable as to its environmental effects. As a result it is seen as desirable to remove the solid portions in this type of marine discharge before discharging the effluent water to a storm drain or other fluid handling structure. All of the prior art cited above has large volumetric flows of effluent, making portable on-line filtration unfeasible. A different type of structural design is required to remove the solid material from underwater structures with a minimum of effluent water being incorporated as the carrier. Because the brush design of SCAMP has been proven superior in growth removal without damaging hull coatings, incorporating this type of brush in a new cleaning design which more efficiently scavenges the dislodged marine growth is seen as desirable.
In another disclosure relative to non-destructive testing, U.S. Pat. No. 4,814,705 discloses a non-destructive testing device which is held attracted to a ferrous metal surface by an electromagnet, and is capable of moving along the surface. In this device, the magnet serves the dual function of attractor to the substrate and of inducing a magnetic field into the substrate for providing metal plate thickness measurements. The flux leakage level of the magnetic field can be measured by a Hall effect sensing device. This invention can be used for metal thickness measurements of relatively large areas of metal plating such as are found in land based petroleum storage tanks. Although fairly well adapted for above water environments, it suffers from the liability of having the poles of the magnet in constant, very close proximity to the metal substrate to facilitate the requisite attraction and magnetic induction of the substrate. This design produces large amounts of metal filings and metallic debris being collected by and attached to the magnet in short periods of time, which need to be periodically removed to facilitate continued effective operation of the device. This is not always possible in underwater operations, due to the remoteness of the work site from the operating platform and other logistics considerations such as difficulty in navigating to and reacquiring the exact work site, short operating windows due to production schedules, departure schedules of the vessel being worked on, etc. The design of this invention has the additional liability of being poorly adapted to uneven surfaces. Because the magnet must be in intimate contact with the work surface to provide adequate attraction to it, there is less ground clearance for the vehicle to traverse irregularities in the substrate. As a result if the surface has significant irregularities, such as dents and high spots, the magnet often makes physical contact with the substrate and subsequently jams the vehicle in place, effectively rendering it inoperable. Most ships and marine structures have uneven surfaces due to high spots on weld seams, weather and sea effects, tug damage, etc., which often cannot be accurately quantified beforehand, making this design unattractive for underwater applications. Additionally, whenever the clearance between the magnet and substrate varies markedly the accuracy of the measurements gained is influenced, making the measurements less reliable. There is an evident need for a structural design which will correct these liabilities and deficiencies.
Another vehicle which uses a Hall effect sensor to measure metal loss is disclosed in U.S. Pat. No. 4,573,013. This disclosure describes a vehicle which is used to inspect the steel reinforcing members in prestressed concrete beams. The above water portions of bridges are routinely inspected using this type of tool, but has not been adapted to the underwater environment. Underwater corrosion of reinforcing members in bridges is a critical problem which reduces the structural soundness of the bridge. There is an unanswered need for an ROV which can attach itself to the underwater portions of concrete structures for reinforcing member inspections periodically. In addition, similar tools to measure metal soundness in concrete bridges, based on new radar technologies, have recently been introduced into the marketplace and are well adapted to incorporation in the design of the present invention.
The prior art discussed above, having wheeled means of propulsion along an underwater surface, all suffer from the same traction problems to a greater or lesser degree, because attachment of marine algae and grass to all underwater surfaces makes them slippery and difficult to gain traction on for an underwater vehicle. The added liability of increased frictional resistance due to the seals of an enclosure being in contact with the surface creates an additional traction problem for conventional wheeled vehicles, making conventional wheel designs unsuitable for vehicles incorporating enclosures which press against the structure and are to be moved while doing so. Marine shell encrustation, such as barnacles, add to the problem both for the enclosure's forward movement and for the small wheels of the vehicle to climb over them. Traction has proven to be inadequate in the prior art where large barnacles are in common evidence, sometimes preventing the machine from moving forward against the growth, even though all of its wheels are turning as drive wheels. A method of increased traction such as tractor treads to drive underwater vehicles which attach themselves to underwater surfaces is needed. In addition; the need for high maneuverability after the vehicle has attached itself to the substrate has not been met by the prior art, because the existing vehicles are designed for long periods of relatively few turning movements as they progress in horizontal movements in hull cleaning operations with turns to change direction but not to accurately position the machine in a specific location for a viewing or inspection task. Tracked vehicles used for sea bed tasks such as cable burial typically have full length tracks which are not well adapted for high maneuverability in close quarters, which is a requirement of underwater damage inspections of ships and structures. It is evident that an innovative new wheel design is needed for this application.
Relative to vehicles which are capable of adhering to and traversing the side of a ship or other structure and can be either immersed or operated in dry, out of water applications for inspecting, cleaning and painting of ship hulls as well as other tasks, have not addressed the need to navigate while in inverted positions. U.S. Pat. No. 3,960,229 by Shio, discloses a vehicle with full length, tank like electromagnetic treads which will not remain magnetized when the machine's weight pulls the tread away from the wheels, separating the electrical contacts, thus losing attractive force. In addition, this vehicle must be turned by operating one tread while the other is held in a stationary position in the conventional manner used to steer military tanks and construction machinery, which is awkward and difficult on rough surfaces such ship bottoms with large barnacles in evidence, thus interfering with the turning movements and making the vehicle subject to losing adhesion. For manuvering and transiting along small radius curvatures such as pipelines or oil platform jacket legs, spherical wheels are advantageous in that they will roll against the surface through a wide range of diameters. In another disclosure, U.S. Pat. No. 3,609,612 by Tibbling shows several rotating wheels each surrounded by an electromagnet which is held in proximity to the metal substrate by a frame. This type of arrangement requires a space between the electromagnet and the substrate and is subject to jamming against protrusions or uneven surfaces. It is not well adapted for use on underwater surfaces with marine growth or which have been deformed by the elements or have been damaged, and is not a spherical but a round wheel with a flat bottom cross sectionally, making it difficult to turn on short radius curvatures.
Prior art free swimming ROVS have suffered from the inability to perform high quality 3-D laser or other 3-D mapping methods for inspection of damage to structures in preparation for repair element fabrication using raster scanning photogrammetry laser systems, because of the requirement that the operating platform be held perfectly stable for several or more seconds while the mapping acquires an image, even if held against the structure by several robotic arms. A heretofore unanswered need for a method of accurately remotely measuring the boundaries and configuration of damage as a tool for repair planning is hereby disclosed.
In addition, a three dimensional measuring tool which can be carried by an inspection ROV for quickly and easily gaining accurate dimensions of battle and collision damage by physically conforming to the shape of the damage in zero visibility conditions is of value in emergency repair situations where time is of the essence in being able to precisely measure and accurately fabricate closely fitting patches to effect the repair. In the past, much trial and error has been used to determine the exact shape of deformed shell plating at the site of battle and collision damage, with divers making countless trips down to the damage site to test a new doubler plate shape for snugness and weldability. This circumstance often evidences itself in littoral regions, with large amounts of suspended particles in the water which may prevent the acquisition of useful, accurate forward looking sonar or 3-D laser mapping data. It is of benefit to provide a simple method of accurately measuring and cataloging the exact shape of damage to the hull to effect timely underwater repairs.
In addition, for navigation and guidance of an ROV and for higher quality telepresence, the combination of forward looking sonar and a stereoscopic laser imaging system is novel as an enabling tool. This system may be combined with various commercial 3-D viewing systems for measurement, identification and discrimination of underwater objects, and various head mounted or free space holographic telepresence systems to enable viewing around the ROV. U.S. Pat. No. 4,010,619 by Hightower et al, discloses a free swimming ROV with an on board sonar system and TV cameras, both of which are used for navigation and guisdance, but the specification mentions nothing about combining them in a sensor fusion system in one array to be used simultaneously. This involves the steps of combining the images in a composite, then writing software and applying it to an application to integrate the two images before the images can be integrated in a way that can be understood. In another prior art disclosure, U.S. Pat. No. 4,502,407 by Stevens, shows a free swimming ROV with several robotic arms attached, but no mention of a sonar transducer being attached to either arm for navigation, guidance or for damage studies in littoral regions is mentioned in the specification.
Relative to robotically controlled welding using robotic arms, x-y coordinate movable torches, and wheeled movable vehicles, there is a long list of prior art for above water applications, but no underwater welding robots have been developed which can attach to and freely traverse an underwater surface while remaining attached to it, which is a requirement to maintain the stability needed to complete high quality robotic welds. Due to the nature of the underwater environment, the present level of technological development of free swimming ROV'S to hold station in a current or high sea state is inadequate to provide a work platform for high quality, precise task accomplishment of the above types which require steadiness and controlled movements. An ROV which can attach itself to an underwater work surface is needed if high quality underwater task accomplishment such as welding and related inspections and mapping of the underwater body of ships and marine structures are to be accomplished. In addition, for underwater cutting, the present invention is specifically well adapted for use with conventional plasma arc cutting torches or the "Spinarc" underwater spark erosion cutting process, manufactured by Spinarc, Inc., Wirtz, Va. For long continuous cutting tasks requiring precise control over the cutting path, any of which may be attached to either a robotic arm or to the interior of the evacuable enclosure and mounted on a linear slide or similar automation system. The present invention is capable of being moved at a controlled rate along a work surface as the cutting operation continues without periodic interruptions for repositioning, making this a versatile and precise tool for robotic underwater cutting tasks. This capability of attaching to a structure is also of value in pipeline operations where excavation underneath the pipe is need for repairs or inspections. The ability to remain perfectly motionless while attached to a pipeline and manipulating an airlift or a jet with a robotic arm to enable the displacement of large masses of soil is seen as an advantage and a heretofore unmet need.
In addition, the need for a buoyancy allocation system which is capable of selectively moving either or both a volume of air for buoyancy, and water for ballast from one location on the ROV to another has not been well developed in prior art. The need to maintain a stable position at an underwater location while suspended in a volume of water for long periods in an inverted, vertical or other component position is enhanced by a system which can adapt to task requirements and can add either ballast or buoyancy at will and place it at a selected location on the ROV. In addition, the need to compensate for weight or twisting moment increases inherent in moving or manipulating heavy objects around underwater is best answered by a system which can compensate for these forces in a passive manner, allowing the thrusters freedom for navigation and guidance needs.
Several prior art patents have created variable buoyancy features, but have not addressed the allocation of buoyancy or ballast. U.S. Pat. No. 5,174,222 by Rogers discloses a simple bellows type buoyancy chamber which may be remotely inflated but is not capable of being robotically moved to another location on the machine while in operation, and will not remain constant in buoyancy as depth changes due to its flexible nature. A prior art disclosure for a hull cleaning machine which has the brushes incorporated with multiple impellers is disclosed in U.S. Pat. No. 4,697,536 by Hirata. This invention is a diver operated vehicle and has no thrusters or other navigation and guidance means incorporated. It shows several floats with movable pistons and springs internally specifically for introduction of air to increase bouyancy when required. It does not have any valving attached to the pistons or other methods of controlling allocation of fluids and gases in the pistons and the specification does not teach that the pistons can be used for bouyancy allocation by adding either air or water to one side or the other of the piston chamber to compensate for heavy loads which the machine may be carrying, or for inverted positions in mid water which require that the machine be navigated for prolonged periods without touching the work surface in an inspection mode using the on board guidance and navigation elements. The need for an inspection or work vehicle which can be selectively buoyed and ballasted and which can retain constant buoyancy as depth changes, and can compensate for dynamic buoyancy changes such as from an evacuable enclosure which is in turn either full of a gas or water, or for tasks involving transport or manipulation of heavy objects, making vast changes in the dynamic capabilities in the machine is hereby addressed.
In addition, a movable weight on board the vehicle made of lead or other heavy metal which can be quickly changed with a heavier or lighter one for specific tasks, and which can be moved from one location to another on the vehicle after installation while the vehicle is in operation and on location is of advantage in the delivery and installation of heavy objects on underwater structures, and for the subsequent inspection or adjustment of the object. In this type of application, the vehicles bouyancy allocation instantally becomes unbalanced if the vehicle has had compensating bouyancy or ballast added for off balance loads or for installations in inverted or other positions. This feature on board an ROV offers the advantage of eliminating or reducing the size of an awkward and bulky bouyancy package attachment to the object to be delivered. The combination of a movable weight system and a bouyancy allocation system provides the ROV with the means to counterbalance the weight of heavy objects which the ROV may be called upon to transport to underwater locations. U.S. Pat. No. 4,455,962 by Gongwer shows a spherical, free swimming ROV with a movable weight to provide attitude control while in operation underwater. However, the specification does not address whether this weight may be used to counterbalance off balance loads which the ROV may be called upon to transport to an underwater location.
Relative to intrinsically safe electrical generating systems and power transmission devices, which are required for ROVS which are used for ballast and cargo tank inspections on ships and other potentially explosive structures, U.S. Pat. No. 4,821,665 by Matthias et al, shows an ROV with an intrinsically safe submersible power generating system which is powered by a flow of hydraulic fluid from the surface. This vehicle is not a surface adhering vehicle and the power generating system requires a separate supply of fluid for a hydraulic motor which turns the generator. In a related disclosure, U.S. Pat. No. 4,808,837 by the same inventor discloses the submersible power generator of the ROV for shipping and general flammable applications. The disclosure does not however suggest its use or adaptation to an unrestricted ambient flow of water to generate electricity.